Technical Field
The present invention relates to compounds that inhibit corrosion of mild steel and methods thereof. More specifically, the present invention relates to compounds containing multiple functional motifs for arresting mild steel corrosion, methods of synthesizing the compounds and methods of preventing corrosion of mild steel with the compounds.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Mild steel is the least expensive and most commonly used among all steel alloys. Mild steel is weldable, very hard and durable, despite the fact that it rusts easily. Containing a maximum of 0.29% carbon, mild steel is able to be magnetized and is used in almost any project that requires a vast amount of metal.
Many of the everyday objects that are created from steel are made using mild steel, including automobile chassis, motorcycle frames and most cookware. Due to its poor corrosion resistance, mild steel must be painted or otherwise protected and sealed in order to prevent rust from damaging it. A light coat of oil or grease is able to seal this steel and aid in rust control.
Most of the pipelines in the world are made of mild steel which not only allows the pipe to be easily welded into place, but also lets the pipeline flex to avoid cracking and breaking under pressure.
The corrosion of mild steel pipelines constitutes a significant portion (˜30%) of the economic losses in the oil and gas industry (W. Durnie, B. Kinsella, R. De Marco, A. Jefferson, Structure activity of oil field corrosion inhibitors, J. Electrochem. Soc. 146 (1999) 1751-1756; F. Bentiss, M. Lagrenee, M. Traisnel, 2, 5-bis(n-pyridyl)-1 3,4-oxadiazoles as corrosion inhibitors for mild steel in acidic media, Corrosion 56 (2000) 733-742; V. S. Sastri, Corrosion Inhibitors, Principles and Application, John Wiley and Sons, Chichester, UK, 1998—each incorporated herein by reference in its entirety). Crude oil itself is corrosive; carbon dioxide, present in gas or injected into oil wells to increase its production, is also corrosive (X. Jiang, Y. G. Zheng, D. R. Qu, W. Ke, Effect of calcium ions on pitting corrosion and inhibition performance in CO2 corrosion of N80 steel, Corros. Sci. 48 (2006) 3091-3108—incorporated herein by reference in its entirety). Mild steel also undergoes severe corrosive attack during industrial acid cleaning.
The corrosive attack in the HCl medium is explained using the following Reactions 1-5 occurring at anode and Reactions 6-9 occurring at cathode (M. Morad, J. Morvan, J. Pagetti, ‘Proceedings of the 8th European Symposium on Corrosion Inhibitors (8 SEIC)’, Ann. Univ. Ferrara, N. S., Sez V, Suppl: N. 10:159, 1995; K. Aramaki, N. Hagiwara, H. Nishihara, The synergistic effect of anions and the ammonium cation on the inhibition of iron corrosion in acid solution, Corros. Sci. 27 (1987) 487-497—each incorporated herein by reference in its entirety):
Anodic Dissolution of Fe:Fe+Cl−(FeCl−)ads  (Reaction 1)(FeCl−)ads(FeCl)ads+e−  (Reaction 2)(FeCl)ads→FeCl++e−  (Reaction 3)FeCl+Fe2++Cl−  (Reaction 4)(FeCl−)ads+Inh+(FeCl− . . . Inh+)ads  (Reaction 5)Cathodic Evolution of H2:Fe+H+(FeH+)ads  (Reaction 6)(FeH+)ads+e−→(FeH)ads  (Reaction 7)(FeH)ads+H++e−→Fe+H2  (Reaction 8)Fe+Inh+(FeInh+)ads  (Reaction 9)
The detrimental reactions are retarded by consecutive adsorption of a chloride ion and a cationic inhibitor (Inh+) as described in Reaction 5 which restricts Reactions 2-4. The corrosion by cathodic evolution of hydrogen, on the other hand, can be minimized by effective competition of the Inh+ with H+ (Reaction 6 vs. Reaction 9).
The nature of anions is known to influence the efficiency of corrosion inhibition by ammonium salts (F. Bentiss, M. Lagrenee, M. Traisnel, J. C. Hornez, The corrosion inhibition of mild steel in acidic media by a new triazole derivative, Corros. Sci. 41 (1999) 789-803—incorporated herein by reference in its entirety). While anions are excellent inhibitors in HCl, they are, however, poor inhibitors in H2SO4 (T. Murakawa, N. Hackerman, The double layer capacity at the interface between iron and acid solutions with and without organic materials, Corros. Sci. 4 (1964) 387-397—incorporated herein by reference in its entirety). The positive surface charge of iron in both acidic media, because of the corrosion potential Ecorr being more positive than the potential for zero charge (PZC) Eq=0, discourages the adsorption of organic cations (L. I. Antropov, Zhurnal Fizicheskoi Khimii, The application of the potential scale to the problem of the corrosion and protection of metals, 37 (1963) 965-978—incorporated herein by reference in its entirety). However, the stronger adsorbability of the Cl− in compare to SO42− (S. Rengamani, S. Muralidharan, M. A. Kulandainathan, S. V. Iyer, Inhibiting and accelerating effects of amino phenols on the corrosion and permeation of hydrogen through mild-steel in acidic solutions, J. Appl. Electrochem. 24 (1994) 355-360; J. O'M. Bockris, B. Yang, The mechanism of corrosion inhibition of iron in acid solution by acetylenic alcohols, J. Elctrochem. Soc. 138 (1991) 2237-2252; W. J. Lorenz, Zeitschrift fuer Physikalische Chemie (Leipzig), Theory of partial charge transfer reactions 244 (1970) 65-84—each incorporated herein by reference in its entirety), shifts the PZC (Eq=0) to more positive values than the Ecorr thereby allowing the electrostatic adsorption of inhibitor ions Inh+. The film of (FeCl− . . . Inh+)ads imparts protection against corrosive HCl media. The inhibitive efficiencies of organic cationic inhibitors in H2SO4 media increases significantly in the presence of halide ions (A. Popova, E. Sokolova, S. Raicheva, M. Chirstov, AC and DC study of temperature effect on mild steel corrosion in acid media in presence of benzimidazole derivatives, Corros. Sci. 45 (2003) 33-58—incorporated herein by reference in its entirety). Since the first introduction of isoxazolidines to the corrosion literature (S. A. Ali, M. T. Saeed, S. U. Rahman, The isoxazolidines: a new class of corrosion inhibitors of mild steel in acidic medium, Corros. Sci. 45 (2003) 253-266—incorporated herein by reference in its entirety), continued efforts have established that these compounds bearing long chain hydrophobic substituents are effective inhibitors both in H2SO4 and HCl media (S. A. Ali, A. M. El-Shareef, R. F. Al-Ghamdi, M. T. Saeed, The isoxazolidines: the effects of steric factor and hydrophobic chain length on the corrosion inhibition of mild steel in acidic medium, Corros. Sci. 47 (2005) 2659-2678; S. A. Ali, H. A. Al-Muallem, M. T. Saeed, S. U. Rahman, Hydrophobic-tailed bicycloisoxazolidines: A comparative study of the newly synthesized compounds on the inhibition of mild steel corrosion in hydrochloric and sulfuric acid media’, Corros. Sci. 50 (2008) 664-675; S. A. Ali, H. A. Al-Muallem, S. U. Rahman, M. T. Saeed, Bis-Isoxazolidines: a new class of corrosion inhibitors of mild steel in acidic media, Corros. Sci. 50 (2008) 3070-3078—each incorporated herein by reference in its entirety). Diallylamines bearing long chain hydrophobe and alkyne substituents also imparted excellent protection in both acidic media (S. A. Ali, A. J. Hamdan, A. A. Al-Taq, S. M. J. Zaidi, M. T. Saeed, In search of a functionality for an efficient inhibition of mild steel corrosion both in HCl and H2SO4, Corros. Eng. Sci. Technol. 46 (7) (2011) 796-806—incorporated herein by reference in its entirety). The mechanisms through which the corrosion inhibitors function have been ascribed to adsorption processes on either or both the anodic or cathodic sites. The formation of a good protective film (coating) on the metal surface essentially requires an inhibitor molecule to have (1) a hydrophilic polar end (e.g. cationic group), (2) a long alkyl chain to form a hydrophobic barrier, and (3) functional group like alkyne or a cinnamyl moiety which can undergo H atom-initiated polymerization between the adsorbed inhibitor molecules (F. B. Growcock, W. W. Frenier, V. R. Lopp, Proc. 6th Eur. Symp. on ‘Corrosion inhibitors’, Ferrara, Ann. Univ. Ferrara, N. S., Sez V, Suppl. 7, 1185, 1980; D. Jayaperumal, S. Muralidharan, P. Subramanium, G. Venkatachari, S. Senthilvel, Propargyl alcohol as hydrochloric acid inhibitor for mild steel-temperature dependence of critical concentration, Anti-Corros. Methods Mater. 44 (1997) 265-268; F. B. Growcock, Inhibition of Steel Corrosion in HCl by Derivatives of Cinnamaldehyde: Part I. Corrosion Inhibition Model, Corrosion 45(12) (1989) 1003-1007—each incorporated herein by reference in its entirety). Many inhibitors undergo physisorption on the metal surface (S. Muralidharan, K. L. N. Phani, S. Pitchumani, S. Ravichandran, S. V. K. Iyer, Polyamino-Benzoquinone Polymers: A New Class of Corrosion Inhibitors for Mild Steel, J. Electrochem. Soc. 142 (1995) 1478-1483—incorporated herein by reference in its entirety), while inhibitors having non-bonded and π-electrons may undergo chemisorption (N. Hackerman, R. M. Hurd, Proc. Int. Cong. on ‘Metallic corrosion’, London, Butterworth, (1962) 166-170—incorporated herein by reference in its entirety).
The CO2 corrosion is explained using the reactions described in Reactions 10-16 below. It is the carbonic acid (not the dry CO2) which, at the same pH, has been found to be more aggressive than hydrochloric acid for attacks to mild steel pipelines as a result of Reactions 12-16 shown below (G. Zhang, C. Chen, M. Lu, C. Chai, Y. Wu, Evaluation of inhibition efficiency of an imidazoline derivative in CO2-containing aqueous solution, Mater. Chem. Phys. 105 (2007) 331-340; U. Lotz, L. Van Bodegom, C. Ouwehand, The effect of type of oil or gas condensate on carbonic acid corrosion, Corrosion 47 (1991) 635-644; K. Chokshi, W. Sun, S. Nesic, Iron carbonate scale growth and the effect of inhibition in CO2 corrosion of mild steel, NACE International Corrosion Conference & Expo, Paper No. 05285, 2005—each incorporated by reference in its entirety):CO2(g)CO2(aq)  (Reaction 10)CO2(aq)+H2O H2CO3(aq)HCO3−(aq)+H+(aq)  (Reaction 11)Fe(s)+2H2CO3(aq)Fe(HCO3)2(aq)+H2(g)  (Reaction 12)Fe(s)+2H+(aq)Fe2+(aq)+H2(g)  (Reaction 13)Fe2+(aq)+2H2O Fe(OH)2(s)+2H+(aq)  (Reaction 14)Fe(OH)2(s)FeO(s)+H2O  (Reaction 15)Fe(HCO3)2(aq)FeCO3(s)+H2CO3(aq)  (Reaction 16)
Corrosion inhibitors bearing hetero-atoms of N, O, P, or S having non-bonded electrons and long chain hydrophobes are used when the formation of a protective (FeCO3) layer (F. Farelas, M. Galicia, B. Brown, N. Nesic, H. Castaneda, Evolution of dissolution processes at the interface of carbon steel corroding in a CO2 environment studied by EIS, Corros. Sci. 52 (2010) 509-517; K. Videm, A. Dugstad, Corrosion of carbon-steel in an aqueous carbon-dioxide environment. Part 1: solution effects, Mater. Performance 28 (1989) 63-67—each incorporated herein by reference in its entirety), which helps reduce the corrosive attack, is not favorable (Y. J. Tan, S. Bailey, B. B. Kinsella, An investigation of the formation and destruction of corrosion inhibitor films using electrochemical impedance spectroscopy (EIS), Corros. Sci. 38 (1996) 1545-1561; V. Jovancicevic, S. Ramachandran, P. Prince, Inhibition of carbon dioxide corrosion of mild steel by imidazolines and their precursors, Corrosion 55 (1999) 449-455; F. Bentiss, M. Triasnel, H. Vezin, M. Lagrenee, Linear resistance model of the inhibition mechanism of steel in HCl by triazole and oxadiazole derivatives: Structure-activity correlations, Corros. Sci. 45 (2003) 371-380—each incorporated herein by reference in its entirety). FeCO3 is less soluble at high temperatures and pH values; as such higher temperatures usually decrease the corrosion rate because of formation of the more stable surface films (S. L. Wu, Z. D. Cui, F. He, Z. Q. Bai, S. L. Zhu, X. J. Yang, Characterization of the surface film formed from carbon dioxide corrosion on N80 steel, Mater. Lett. 58 (2004) 1076-1081; E. W. J. van Hunnik, B. F. M. Pots, E. L. J. A. Hendriksen, The Formation of protective FeCO3: Corrosion Product Layers in CO2 Corrosion, Corrosion/96, Paper No. 6, NACE, Houston, Tex., 1996; S. Nesic, K. L. J. Lee, A mechanistic model for carbon dioxide corrosion of mild steel in the presence of protective iron carbonate films-part 3: film growth model, Corrosion 59 (2003) 616-627—each incorporated herein by reference in its entirety). Electron-rich imidazolines are extensively used to minimize corrosion in the oil and gas industry (X. Liu, S. Chen, H. Ma, G. Liu, L. Shen, Protection of iron corrosion by stearic acid and stearic imidazoline self-assembled monolayers, Appl. Surf. Sci. 253 (2006) 814-820; X. Liu, P. C. Okafor, Y. G. Zheng, The inhibition of CO2 corrosion of N80 mild steel in single liquid phase and liquid/particle two-phase flow by amino ethyl imidazoline derivatives, Corros. Sci. 51 (2009) 744-751; P. C. Okafor, X. Liu, Y. G. Zheng, Corrosion inhibition of mild steel by ethylamino imidazoline derivative in CO2-saturated solution, Corros. Sci. 51 (2009) 761-768; F. Farelas, A. Ramirez, Carbon dioxide corrosion inhibition of carbon steels through bis-imidazoline and imidazoline compounds studied by EIS, Int. J. Electrochem. Sci. 5 (2010) 797-814; X. Liu, Y. G. Zheng, Effect of hydrophilic group on inhibition behaviour of imidazoline for CO2 corrosion of N80 in 3% NaCl solution, Corros. Eng. Sci. Tech. 43 (2008) 87-92; M. W. S. Jawich, G. A. Oweimreen, S. A. Ali, Heptadecyl-tailed mono- and bis-imidazolines: A study of the newly synthesized compounds on the inhibition of mild steel corrosion in a carbon dioxide-saturated saline medium” Corros. Sci. 65 (2012) 104-112—each incorporated herein by reference in its entirety).
Inadequate unraveling of the complex mechanism of CO2 corrosion has become the impediment in the design of new inhibitors (A. Edwards, C. Osborne, S. Webster, D. Klenerman, M. Joseph, P. Ostovar, M. Doyle, Mechanistic studies of the corrosion inhibitor oleic imidazoline, Corros. Sci. 36 (1994) 315-325; G. McIntire, J. Lippert, J. Yudelson, The effect of dissolved CO2 and O2 on the corrosion of iron, Corrosion 46 (1990) 91-95—each incorporated herein by reference in its entirety). The effective commercial formulations used in the corrosion inhibition of oil field steel are mixtures of surface-active compounds: N-containing compounds, acetylenic compounds, surfactants, and aldehydes. Accordingly, in order to help alleviate economic loss as a result of mild steel corrosion, it will be desirable to design corrosion inhibitor compounds that combine the important functional features such as cationic charges, hydrophobic environment, alkyne, and cinnamyl motifs.